1. Field of the Invention
The present invention is directed to the field of D.C. motor manufacturing and more specifically to the area of machining the commutator portion of such motors.
2. Description of the Prior Art
Both mechanical and laser machining processes have been used to undercut insulative material from the area between commutator bars of a D.C. motor armature. Mechanical systems involve friction grinding and removal of the insulation. These systems are relatively slow and require periodic maintenance or replacement of the grinding tool. While laser ablating systems hold great promise for lowering the costs of performing the insulation removal step in the motor manufacturing process, prior art systems appear to be inefficient.
U.S. Pat. No. 4,329,564 discloses a method for laser undercutting the insulation between commutator bars. In that patent, the armature is mounted on a motor driven x-y table for movement and high speed rotation of the armature with respect to a fixed laser beam. The beam is focused a distance above the surface and the angle of incidence is at a significant angle with respect to the perpendicular of the surface of the armature so that the incident beam is wide enough to impinge on both the insulative dielectric and the adjacent commutator bar.
There is a great need to overcome the complicated and costly x-y type table configuration shown in the prior art and to provide a low maintenance, high speed alternative in order to achieve efficiencies suitable for use in a high volume manufacturing process.